In situ STM Studies of Electrochemically Polished Cd(0001) Electrode in 1-ethyl-3- methylimidazolium tetrafluoroborate

The in situ scanning tunneling microscopy (STM) and electrochemical impedance spectroscopy studies of electrochemically polished Cd(0001) electrode have been performed in the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF 4 ) ionic liquid within electrode potential region from -1.6 V to -0.9 V (vs. Ag|AgCl|EMImBF 4 ). The in situ STM data show that there are no quick surface reconstruction processes and the ideal surface structure of Cd(0001), very similar to that previously observed in aqueous electrolyte, has been established

The metal – ionic liquid interface as characterized by impedance spectroscopy and in-situ scanning tunneling microscopy

We summarize our results of electrochemical measurements carried out on inert or close-to-inert metals in ionic liquids, with the aim to explore the metal | ionic liquid interface structure. To this we used electrochemical methods: cyclic voltammetry, impedance spectroscopy, potential of zero total charge measurements and structure-sensitive techniques, such as in-situ scanning tunneling spectroscopy. The studied systems were mostly single crystals of noble metals in imidazolium-based ionic liquids. The two main findings are: (i) in the potential window where no Faradaic reactions occur, the interfacial capacitance exhibits a frequency dependence due to double-layer rearrangement processes and (ii) in certain cases ordered anion and cation structures exist at the interface

Ionic liquids at electrified interfaces

Until recently, “room-temperature” (<100–150 °C) liquid-state electrochemistry was mostly electrochemistry of diluted electrolytes(1)–(4) where dissolved salt ions were surrounded by a considerable amount of solvent molecules. Highly concentrated liquid electrolytes were mostly considered in the narrow (albeit important) niche of high-temperature electrochemistry of molten inorganic salts(5-9) and in the even narrower niche of “first-generation” room temperature ionic liquids, RTILs (such as chloro-aluminates and alkylammonium nitrates).(10-14) The situation has changed dramatically in the 2000s after the discovery of new moisture- and temperature-stable RTILs.(15, 16) These days, the “later generation” RTILs attracted wide attention within the electrochemical community.(17-31) Indeed, RTILs, as a class of compounds, possess a unique combination of properties (high charge density, electrochemical stability, low/negligible volatility, tunable polarity, etc.) that make them very attractive substances from fundamental and application points of view.(32-38) Most importantly, they can mix with each other in “cocktails” of one’s choice to acquire the desired properties (e.g., wider temperature range of the liquid phase(39, 40)) and can serve as almost “universal” solvents.(37, 41, 42) It is worth noting here one of the advantages of RTILs as compared to their high-temperature molten salt (HTMS)(43) “sister-systems”.(44) In RTILs the dissolved molecules are not imbedded in a harsh high temperature environment which could be destructive for many classes of fragile (organic) molecules

Ioonide adsorptsioonikineetika Bi monokristalli tahkudel vesilahustes ja ioonsetes vedelikes

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Erinevate keemiliste protsesside omaduste uurimisega on keemikud tegelenud sajandeid. Füüsikaline elektrokeemia on teadusharu, mis keskendub keemiliste reaktsioonide ja protsesside füüsikaliste omaduste väljaselgitamisele. Antud doktoritöö teemaks on ioonide adsorptioonikineetika uurimine vesilahustes ning ioonsetes vedelikes metallelektroodil, milleks on vismut. Adsorptsioon on pinnanähtus, mille puhul osakesed kogunevad molekulaarjõudude toimel tahkele pinnale, milleks antud juhul on vismutelektroodi pind. Adsorptsiooniprotsessi toimumise kirjeldamisel on suur tähtsus, kuna adsorptsiooniprotsessid mõjutavad mitmete keemiliste protsesside kiirust, milleks on metallide lahustumine, elektrokeemiline korrosioon, elektrosadestamine, elektrosüntees ja –analüüs, elektrilise kaksikkihi kondensaatoris ja kütuseelemendis toimuvad protsessid. Näiteks efektiivseks korrosiooni inhibeerimiseks kasutatakse tihtipeale orgaanilisi aineid, mis koos spetsiifiliselt adsorbeeruvate katioonidega on võimelised moodustama stabiilseid kompaktseid adsorptsoonikihte. Samuti on leitud, et mõningate elektrosünteesiprotsesside korral on oluline roll foonelektrolüüdina kasutatava lahuse keemilisel koostisel ning mõningad protsessid võivad oluliselt kiireneda spetsiifiliselt adsorbeeruvate katioonide, aga ka anioonide juuresolekul süsteemis. Antud töös näidati, et jodiidiooni adsorptsioonikineetika sõltub elektroodile antud potentsiaalist, jodiidioone sisaldava lahuse kontsentratsioonist ning süsteemile rakendatavast vahelduvvoolu sagedusest. Viimastel aastatel on aktiivse uurimise alla võetud uus ainete klass- ioonsed vedelikud. Ioonsed vedelikud koosnevad nagu nimigi ütleb põhiliselt ioonidest. Ioonsetel vedelikel on rida omadusi, mis lubavad neid kasutada uute tehnoloogiliste lahenduste väljaarendamisel. Antud töös uuriti ioonsete vedelike elektrokeemilisi omadusi ja kasutamise võimalikkust superkondensaatorites.Properties of chemical reactions have been in interest of chemists for decades. Physical electrochemistry is a branch of chemistry that studies physical properties of chemical reactions and charge transfer processes. The main aim of this work was to study the adsorption kinetics of iodide ions and to characterize properties of adsorption kinetics of ionic liquid at bismuth electrode surface. Adsorption is the process of attraction of atoms or molecules (generically known as "monomers") from an adjacent gas or liquid phase to an exposed solid surface. Adsorption processes affect crucially characteristics of heterogeneous electrochemical processes such as anodic dissolution, electrochemical corrosion, electrodeposition, electrosynthesis and electroanalyses. Adsorption processes are important in electric double layer capacitors and fuel cells. Nature of surface active substances as well as ingredients of solutions and crystallographic structure of electrode affect significantly adsorption process kinetics and structure of electrical double layer. Therefore adsorption of inorganic and organic ions, neutral molecules on metal electrodes (poly and mono crystallic), as well as micro- porous carbon electrodes from aqueous and nonaqueous solutions has been studied by electrochemists of Tartu University. In this work it has been pointed out that adsorption of iodide ion depends on the electrode potential applied, on the concentration of solution that contains iodide ions and on ac frequency applied. To date, most chemical reactions have been carried out in electrolytes dissolved in molecular solvents. Recently, however, a new class of chemical reactants has emerged— known as ionic liquids. These substances are fluid at room temperature, and consist mainly of ionic species. They have many fascinating properties which make them of fundamental interest to all chemists, since both the thermodynamics and kinetics of reactions carried out in ionic liquids are different to those in conventional molecular solvents. One of the aim of this work was to establish the properties of electrical double layer at Bi(111) | ionic liquid interface